This invention relates generally to humidifiers and, more specifically, to portable humidifiers intended for domestic use.
Various types of humidifiers are used to increase the humidity in the home environment. With respect to portable humidifying appliances, they may be broken down broadly into three categories, one being the evaporating type, one being the steaming type, and the last being the misting type. Evaporating type humidifiers typically use belts or pads to increase the rate of evaporation of the water from the liquid to the vapor state. Steaming humidifiers, or vaporizers, generally are used to achieve very high humidification levels by raising the water""s temperature above its boiling point. Misting humidifiers use mechanical means to atomize water into small droplets which are dispersed by a fan. The present invention is most closely related to humidifiers of the steaming and evaporating types.
Examples of various prior-art steaming humidifiers are disclosed in U.S. Pat. Nos. 5,067,169, 5,131,070, 5,133,044, and 5,143,460. All of these humidifiers are characterized by disclosing humidification means in which a heating element hangs into a water reservoir to cause boiling of the water in the reservoir. This boiling results in vaporization of the water from the reservoir, but characteristically leaves behind the minerals and impurities from the water to collect on the heating element as slag which thereby diminishes the element""s performance and efficiency.
Examples of various prior art evaporative humidifiers are disclosed in U.S. Pat. Nos. 5,034,162 and 5,108,663. These humidifiers are characterized by disclosing humidification means in which an absorbant and porous pad is placed partially in a water reservoir and partially in an air stream to cause wicking of the water from the reservoir into the airstream. This results in evaporation of the water from the reservoir into the airstream, but is characteristically inefficient as the water and the porous pads are maintained at room temperature. Additionally, the evaporation of water from the pads causes a temperature drop in the exhausting humidified air which is often undesireable in the home environment.
The object of this invention, therefore, is to provide an improved portable humidifier for use in domestic applications.
The present invention is a portable humidifier including a base defining a water supply cavity; a liquid supply means supported on the base and having a discharge opening communicating with the supply cavity and adapted to maintain a given level of liquid therein; and an humidification unit removably mounted on the base and comprising an electrically energized heater within a porous fabric wicking sleeve projecting into the cavity and adapted to efficiently and rapidly induce warm evaporation of the water, and a vapor passage having a receiving end communicating with the cavity so as to receive vapor therefrom and a discharge end for discharging the vapor received from the cavity into the surrounding environment.
According to one feature of the invention, the porous fabric wicking sleeve pulls water, including its minerals and impurities, from the cavity by capillary action to the surface of the heating element, where it is rapidly evaporated leaving those impurities and minerals in the sleeve.
According to another feature, the porous fabric wicking sleeve is easily removable from the heating element. For that reason cleaning of the boiler cavity is simplified and the heating element is kept clean and operating efficiently. The sleeve can easily be removed and regularly washed to remove those impurities and minerals. This feature further also enhances the evaporation efficiency of the unit.
According to another feature, the heating element preheats the water to increase the rate of evaporation, and the heating element also increases the temperature of the exhausted airstream to overcome the temperture drop otherwise inherent in evaporative humidifiers.
According to another feature, during normal operation, the wetted wicking sleeve remains at approximately 100 C degrees, the boiling temperature of water, and the heating element""s surface temperature is thereby regulated. When the supply of water is depleted or the wicking action of the sleeve is reduced, such as by deterioration or excessive residue accumulation, the heating element will realize a sudden increase in surface temperature. A temperature-limiting device in thermal communication with the heating element is thereby triggered to de-energize the heating element and safely disable the humidifier. This same temperature-limiting device also senses the rise in temperature that occurs when the humidification unit is removed from the base and the wick subsequently dries, and thereby serves and a safety shut-off for preventing use of the humidifier when it is not properly assembled.